The invention relates to an opto-electronic method and system for remotely detecting physical magnitudes by means of sensors each of which includes a sensitive element whose spectral transmission varies as a function of the physical magnitude to be measured, said sensors being illuminated by an incoherent light beam and transmitting light signals to spectrum analyzer means.
Since optical fibers have become available, it has become common to use changes in spectral transmission in a medium for the purpose of remotely detecting variation in a physical magnitude such as temperature, chemical composition, magnetic field, etc. . . .
In particular, there exist sensors based on thermochromic solutions in which temperature changes give rise to large changes in the absorption spectrum of the sensitive medium. An example of an embodiment of such a sensor is described in the article by M. Breci et. al. entitled "Thermochromic Transducer Optical Fiber Sensor", 2nd International Conference on Optical Fiber Sensors Sept. 5-7 1984.
Sensors also exist based on a semiconductor etalon in which temperature variations in the sensitive medium cause the edge of the absorption band to move. A sensor of this type is described in the article by K. Kyuma, S. Tai, T. Sawada and M. Nunoshita, entitled "Fiber Optic Instrument for Temperature Measurement", IEEE, QE-18, 676, 1982.
There also exist colorimetric type sensors in which variations in the composition of a binary mixture give rise to variations in its tristimulus values. A sensor of this type is described in French Pat. No. 85 08 550 dated June 6, 1985.
Present methods do not make it possible to multiplex information from several identical sensors of the above-mentioned type simply on a single optical fiber in which the spectrum carriers used would be all mixed together.